1. Field Of The Invention
The invention pertains to apparatus for trimming at least one lateral edge of an advancing continuous sheet and, more particularly, to apparatus for continuously trimming the apertured lateral edges of continuous sheet print medium in a printer.
2. Description Of The Prior Art
Print medium for high-speed line printers typically includes a continuous sheet of imprintable material, such as paper, fed from a paper supply roll or folded pack and advanced through a printer by drive tractors having peripheral teeth for engaging pre-formed spaced apertures linearly disposed along the lateral edges of the sheet. As the sheet is advanced through the printer, alphanumeric characters reflecting stored data, such as from a computer, are printed on the main body of the sheet as hard copy output. Typically, the apertured lateral edges of the sheet are separated from the main body of the sheet by a linear perforation extending parallel to the lateral edges for allowing the lateral edges to be separated from the main body by manually tearing along the perforations after the sheet has exited the printer. The process of separating the lateral edges of the sheet from the main body by hand is very tedious and time consuming. Care must be taken to avoid tearing or otherwise damaging the main body of the sheet to preserve the readability and clarity of the imprinted data. Moreover, the manual tearing process becomes even more difficult when large volumes of print-out are involved and is incompatible with the high-speed characteristics of state of the art line printers.
Although devices for trimming the side edges of computer print-out sheet have been proposed, such devices possess numerous drawbacks and limitations. For example, U.S. Pat. No. 2,311,051 discloses a strip feeding attachment for a tabulating machine including a slitter blade held by a setscrew in a clamped position engaging an advancing strip of material to slit the feed bands from the main body of the strip. Various other devices for trimming at least one of the lateral edge of a continuously advancing sheet of material are shown in U.S. Pat. Nos. 4,611,518 to Hildebrandt, 4,572,686 to Tanaka, 4,423,975 to Krenz and 3,937,377 to Schueler.
Prior art edge trimmers fail to satisfy the requirements for an effective, safe, selectively operable trimmer that can be inexpensively produced and easily installed or retrofitted on printers. To this end, prior art edge trimmers, as exemplified by the above patents, have the disadvantages of having relatively complex mechanisms that are extremely difficult, if not impossible, to install on printers of the type commonly used with computers, of being expensive to manufacture and of being bulky and requiring substantial space as well as presenting exposed cutting members.